Advanced air and oil circuit architecture for turbomachine

ABSTRACT

The present invention relates to a system for lubricating a turbomachine comprising at least one enclosure, called non-ventilated, with members to be lubricated and an air-oil mixture, said enclosure being closed and pressurized using dynamic pressure seals supplied with compressed air to create an airflow from the outside toward the inside of the enclosure, said enclosure comprising an outlet for conveying the air-oil mixture toward an air/oil separator, said separator being provided with an suction function favoring the flow of the air-oil mixture between the enclosure and the separator, characterized in that the lubrication system comprises additional suction means.

FIELD OF THE INVENTION

The present invention relates to a lubrication system for a turbomachine, and more particularly, relates to the air and oil circuits of the lubrication system.

TECHNOLOGICAL BACKGROUND

An aeronautic turbomachine comprises many elements that must be lubricated and cooled; these are in particular the ball bearings used to support the rotating shafts, and gears. These elements are contained in closed or sealed zones called enclosures.

The rolling bearings, gears and bearings installed in the enclosures are lubricated by oil injected at the inlet by a so-called “feed” system and collected at the outlet by a so-called “recovery” system. Pressure seals separate the enclosures from the other parts of the turbomachine and are pressurized using air coming from a portion of the turbomachine called “compressor”. The pressurization of the seals allows to prevent an oil leak from the enclosure toward the rest of the engine through the seals by causing a constant flow of air entering from the outside toward the inside of the enclosure while forcing the oil back toward the inside. These so-called “dynamic” joints therefore allow to contain in the enclosures the air-oil mixture thus formed. This air flow taken from the turbomachine depends on the effectiveness of the dynamic seals and penalizes the output of the turbomachine. Most of the air introduced into the enclosures is discharged to the outside of the turbomachine using a specific circuit intended to de-oil it and monitor the pressure of the enclosure; the enclosures are then said to be “ventilated.” The oil having served for the lubrication in the enclosures is recovered at the bottom of the enclosure by a recovery system via another specific circuit. In order to ensure complete drying of the enclosure, a small portion of the air introduced into the enclosures is also sucked up by these systems and the air-oil mixture thus recovered must be separated before the purified oil is returned to the tank.

One drawback of a so-called “ventilated” architecture is the need to bleed a non-negligible quantity of air compressed by the turbomachine to pressurize the enclosures. A ventilated architecture also consumes considerable lubrication oil because the efficiency of the de-oiling is a decreasing function of the airflow.

There are architectures with so-called “non-ventilated” enclosures where all the air entering through the seals is extracted by the oil-recovery system.

Document EP 1 933 077 A1 has such an architecture. It involves a system for lubricating a turbomachine in which a low airflow is injected through the pressure seals to pressurize the enclosures. All of the air and oil introduced into the enclosures is recovered at the outlet (bottom portion of the enclosures) and conveyed toward the air/oil separator by gravity and by the pressure difference between the inside of the enclosures and the separator. It is provided in this system to integrate a pumping function in the air/oil separator to draw the air-oil mixture toward it. Such a function may be made necessary in the case of too little pressurization in the enclosures. The drawback of this architecture is the risk that one single pumping function is not efficient enough for an air-oil mixture under certain limit conditions, such as at low rating when the pressurization is very weak (ground idle case). On the other hand, a single and non-regulated pumping function may also introduce excessively high airflows for some ratings of the engine relative to the need and cause oversizing of the circuits and recovery elements, as well as an over-consumption of oil.

Document US 2005/0217272 A1 discloses a lubrication system with a de-oiler provided with a suction capacity. It involves a traditional architecture where the airflow and the oil flow are recovered by separate systems at the outlet of the enclosure; the suction system is then applied to the airflow only.

Patent application EP 2 199 614 A1 discloses a machine of the centrifuge type 1, called SIPDA (Scavenge Integrated Pump & DesAerator) and illustrated in FIG. 1, comprising means for the suction, pumping, and partial separation of a liquid/gas mixture 2 (in particular oil/air), means for drying and evacuating the separated gas 4 and means for degassing and forcing back the separated liquid 3.

The suction in this air/oil separator is ensured by the wheel 5 at the inlet of the machine, but the presence of a two-phase flow 2 limits the suction performance.

AIMS OF THE INVENTION

The present invention aims to overcome the drawbacks of the state of the art.

In particular, the present invention aims to achieve an advanced architecture for a lubrication system where the air-oil mixture of an enclosure containing the members to be lubricated is recovered by a single circuit that is provided with a sufficient suction capacity and that is configurable according to the rating of the engine.

The present invention more particularly aims to provide an advanced architecture for a lubrication system comprising additional suction means that are operational when the engine works at low rating (ground idle conditions), thereby preventing too much air from being drawn for the engine ratings where the pressurization of the enclosures is sufficient, thereby avoiding an over-consumption of oil.

SUMMARY OF THE INVENTION

The present invention relates to a system for lubricating a turbomachine comprising at least one enclosure, called non-ventilated, containing members to be lubricated and an air-oil mixture, said enclosure being closed and pressurized using dynamic pressure seals supplied with compressed air to create an airflow from the outside toward the inside of the enclosure, said enclosure comprising an outlet for conveying the air-oil mixture toward an air/oil separator, said separator being provided with a suction function favoring the flow of the air-oil mixture between the enclosure and the separator, characterized in that the lubrication system comprises additional suction means.

According to particular embodiments of the invention, the lubrication system comprises at least one or a suitable combination of the following features:

-   -   the additional suction means are arranged before the air/oil         separator;     -   the additional suction means are arranged after the air/oil         separator;     -   the additional suction means are arranged on an air outlet         and/or on an oil outlet of the air/oil separator;     -   the additional suction means comprise at least one venturi;     -   the additional suction means comprise at least one pump of the         axial, volumetric or centrifuge type;     -   the pump and the venturi are arranged on an air outlet of the         air/oil separator;     -   the air/oil separator is a machine of the centrifuge type         comprising means for the suction, pumping, and partial         separation of the air-oil mixture, means for drying and         evacuating the separated air and means for degassing and forcing         back the separated oil;     -   the additional suction means comprise at least one venturi and         at least one pump;     -   the additional suction means are configured to be used only when         the pressurization of the enclosure is insufficient;     -   the additional suction means are configured to be used when the         turbomachine operates at low rating (ground idle);     -   the pump is configured to be possibly bypassed when the         additional suction function is not required;     -   the pump is configured to disengage when the additional suction         function is not required;     -   the venturi is configured to adjust the injected airflow         according to the engine ratings.

The present invention also relates to a turbomachine comprising a lubrication system such as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the SIPDA equipment according to the state of the art.

FIG. 2 shows the evolution of pressure in the lubrication circuit from the compressor until the outlet of the air/oil separator in the presence of additional suction means according to the invention.

KEY

-   (1) Centrifuge machine, also called SIPDA (Scavenge Integrated Pump     & DesAerator) -   (2) Inlet for the air-oil two-phase fluid -   (3) Oil outlet -   (4) Purified-air outlet -   (5) Wheel -   (6) Outside pressure -   (7) Pressure at the outlet of the compressor -   (8) Pressure upstream of the pressure seals -   (9) Pressure in the enclosure -   (10) Pressure at the inlet of the air/oil separator (SIPDA) -   (11) Pressure at the outlet of the air/oil separator (SIPDA) -   (A) Compressor -   (B) Conveyance between the compressor and the enclosure -   (C) Pressure seal -   (D) Conveyance between the enclosure and the air/oil separator     (SIPDA) -   (E) Air/oil separator (SIPDA) -   (F) Conveyance between the air/oil separator (SIPDA) and the outside

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an advanced architecture for a lubrication system in a turbomachine. It more particularly relates to an architecture with one or more non-ventilated enclosures, i.e. an architecture where all the air entering through the pressure seals into the enclosure(s) is extracted by the oil-recovery system. An architecture of this type is, for example, illustrated in patent application EP 1 933 077 A1.

According to the present invention, each enclosure comprising members to be lubricated is preferably fed with a low compressed air flow introduced into the enclosure through pressure seals to pressurize the enclosure, said airflow coming, for example, from a bleed on the low-pressure compressor but also possibly coming from a bleed on the high-pressure compressor. For at least one of the enclosures, the entire mixture of air and oil injected is extracted through a same outlet and is conveyed toward an air/oil separator that is preferably provided with a suction function. For example, the air/oil separating equipment is of the centrifuge type provided with a suction capacity, such as in the SIPDA.

According to the present invention, the lubrication system is provided with additional suction means regulated according to the operating rating of the engine.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

The present invention will be more particularly and, of course, as a non-limiting example, illustrated for a lubrication system comprising an air/oil separator of the SIPDA type.

FIG. 2 shows the evolution of pressure in the lubrication circuit of the aeronautic turbomachine from the outside air intake at the inlet 6 of the compressor A until the outlet 11 of the SIPDA air/oil separator E, at low rating under ground idle conditions and in the presence of an additional suction function. The compressor may be low or high pressure, a low-pressure compressor being preferable. The detail of references 6 to 11 and A to F is given in the key.

The pressurized air recovered at the outlet 7 of the compressor A is conveyed (ref. B) in the enclosures to pressurize the dynamic seals C and ensure a flow toward the inside of the enclosures. The mixture of the air with the lubrication oil achieved in an enclosure is then conveyed (ref. D) toward the SIPDA equipment E so as to separate the air from the oil, convey the air toward the outside of the turbomachine (ref. F) and convey the oil toward a specific tank. The conveyance D of the air-oil mixture between the enclosure and the SIPDA E is achieved owing to the over-pressure generated by the compressor A. In the absence of additional suction means, the problem that arises for certain ratings and, in particular, at low rating such as under ground idle conditions, is that the pressure available in the compressor is not sufficient to overcome the pressure loss generated by the circuit, which results in having an air pressure at the outlet 11 of the SIPDA lower than atmospheric pressure 6, preventing its extraction. This therefore requires that sufficient suction is created to guarantee the evacuation of the air-oil flow at low rating by increasing the pressure at the outlet of the separator 11, using additional suction means, as diagrammatically shown by the arrow in FIG. 2. However, at other ratings, this suction does not need to remain maximal to avoid the over-consumption of oil in the enclosures.

The present invention therefore consists in increasing and potentially modulating the suction capacity of the recovery system, according to the rating of the engine.

The additional suction function may be performed using different devices arranged before or after the air/oil separator.

According to a first embodiment, the additional suction means are arranged at the outlet of the air/oil separator. The fluids are therefore separated before performing the pumping function on at least one of the fluids, preferably air, and thus improving the suction performance of the recovery system. The pumping function may be performed using an axial, volumetric or centrifuge pump or using a venturi using the air from the compressor. Preferably, a centrifuge or axial pump, or a venturi, are arranged on the air outlet of the air/oil separator in order not to increase the airflow in the de-oiler. Thus, in the case of the SIPDA separator, the centrifuge or axial pump is arranged in position 4 in FIG. 1, on the air outlet of the SIPDA separator (for more details on the SIPDA operation, see key and patent application EP 2 199 614 A1).

According to a second embodiment, the additional suction means are arranged before the air/oil separator. Preferably, the additional suction means comprise a venturi.

According to the invention, the different additional suction means are combined within the lubrication system. For example, the lubrication system may comprise at least one pump and at least one venturi, the pump(s) being arranged after the air/oil separator and the venturi(s) being arranged before or after the air/oil separator.

According to the invention, the different means presented above may be implemented permanently or simply provisionally. The additional suction means may be used only when pressurization of the enclosures is insufficient, for example when the turbomachine operates at low rating (ground idle conditions). To that end, the lubrication system may comprise means for regulating the above-mentioned devices, according to the operating rating of the engine.

In the case of a pump, it may be bypassed via a bypass (in particular for a volumetric pump) or may comprise disengaging means so as to limit the airflow in the case when the pumping function is not necessary. In the case of a venturi device, the suction may be modulated by adjusting the airflow injected according to the engine ratings.

ADVANTAGES OF THE INVENTION

The additional suction function according to the invention allows to ensure sufficient vacuum in the enclosures and therefore to guarantee the flow of the air-oil mixture from the engine toward the air-oil separator, for example SIPDA, and guarantee the extraction of the de-oiled air toward the outside of the turbomachine.

It also optionally allows to limit the airflow in the enclosures and therefore to limit the size of the recovery equipment and the oil consumption. 

1. A system for lubricating a turbomachine comprising at least one enclosure, called non-ventilated, with members to be lubricated and an air-oil mixture, said enclosure being closed and pressurized using dynamic pressure seals supplied with compressed air to create an airflow from the outside toward the inside of the enclosure, said enclosure comprising an outlet for conveying the air-oil mixture toward an air/oil separator, said separator being provided with an suction function favoring the flow of the air-oil mixture between the enclosure and the separator, characterized in that the lubrication system comprises additional suction means.
 2. The lubrication system according to claim 1, characterized in that the additional suction means are arranged before the air/oil separator.
 3. The lubrication system according to claim 1, characterized in that the additional suction means are arranged after the air/oil separator.
 4. The lubrication system according to claim 3, characterized in that the additional suction means are arranged on an air outlet and/or on an oil outlet of the air/oil separator.
 5. The lubrication system according to claim 2, characterized in that the additional suction means comprise at least one venturi.
 6. The lubrication system according to claim 3, characterized in that the additional suction means comprise at least one pump of the axial, volumetric or centrifuge type.
 7. The lubrication system according to claim 5, characterized in that the pump and the venturi are arranged on an air outlet of the air/oil separator.
 8. The lubrication system according to claim 1, characterized in that the air/oil separator is a machine of the centrifuge type (1) comprising means for the suction, pumping, and partial separation of the air-oil mixture (2), means for drying and evacuating the separated air (4) and means for degassing and forcing back the separated oil (3).
 9. The lubrication system according to claim 5, characterized in that the additional suction means comprise at least one venturi and at least one pump.
 10. The lubrication system according to claim 1, characterized in that the additional suction means are configured to be used only when pressurization of the enclosure is insufficient.
 11. The lubrication system according to claim 10, characterized in that the additional suction means are configured to be used when the turbomachine operates at low rating (ground idle).
 12. The lubrication system according to claim 6, characterized in that the pump is configured to be possibly bypassed when the additional suction function is not required.
 13. The lubrication system according to claim 6, characterized in that the pump is configured to disengage when the additional suction function is not required.
 14. The lubrication system according to claim 5, characterized in that the venturi is configured to adjust the injected airflow according to the engine ratings.
 15. A turbomachine comprising a lubrication system according to claim
 1. 